Prepare your work area. Primarily, you want an area that is dust-free. You do not need to create a plastic shield around the area, but the least amount of activity and exposure to dust the better.
Brush on two coats of polyurethane with the foam brush. The foam brush prevents fine hairs from getting into the finish. Let the polyurethane cure before applying the second coat. Sand each coat with 220-grit sandpaper.
Brush on two more coats of polyurethane. Let each coat cure. This time use the 400-grit sandpaper dipped in paint thinner and wet sand each coat.
Brush on two more coats of a 50% polyurethane/50% paint thinner mixture. Let each coat cure. This will help get the polyurethane smoothed out and begin the glossy shine. Sand each coat with 400-grit sand paper and buff with bronze wool.